This invention relates to a close-style leak preventing device for a fluid shooting nozzle of an injection molding machine, particularly to one possible to surely prevent raw material inside from leaking out along a hot-material passageway plate and the shooting nozzle of a screw conveying tube of a injection molding machine.
A first known conventional injection molding machine includes a shaft of a stop valve of a hot-material passageway plate, and it is almost of a straight rod shape, fitted around its rear portion with a an annular hollow gasket, as shown in FIG. 9, and placed in a shaft position base. When the stop valve of the hot-material passageway plate and the shaft are closed, the remaining pressure still left in the passageway of the hot-material passageway plate pushes raw material inside fill the hollow gasket so that the gasket is inflated to prevent raw material inside from leaking out along the gap between shaft and the shaft position base. But a long-term use of the hollow gasket may render it weak or exhausted and even damaged by repeated friction with a center hole of the shaft position base, resulting in serious leaking. Besides, the hollow gasket requires high technique in manufacturing, thus elevating its cost.
To eliminate foresaid defects, DWE Company in U.S.A. has worked out a valve system, as shown in FIG. 10. In this valve system, the contact dimensions between a shaft rod (A) and a shaft hole (A1) is lengthened to prolong time for use, but it is still shaped straight, liable to form a gap by long-term friction between them and impossible to avoid liability of leaking, as indicated by the arrow in FIG. 10, and with the shaft possible to be deadlocked.
Further, in a second known conventional injection molding machine, the shaft in a material stop valve of a screw conveying tube, as shown in FIG. 11, has a conical tip like a crayon shape, so after it is fitted in a shooting nozzle, there leaves a gap between the conical end of the stop valve and the shooting nozzle, letting raw material with remaining pressure in the passageway tube of the stop valve leaking out from the gap.
There is also a case of Japanese Patent No. 7-223241, as shown in FIG. 12, and it is also designed to have a straight shaft (B) so that the prevention of leaking caused by high pressure pushing depends only on a common difference between the shaft (B) and the shaft hole (B1). If the common difference is diminished, the shaft (B) may be deadlocked by excessive interference and after used for long, a serious leaking problem will inevitably occur due to a loose condition caused by mutual friction between the shaft (B) and the shaft hole (B1), and if worse, a fire may occur by hot leaking raw material.
The objective of this invention is to offer a leak preventing device for a fluid shooting nozzle of an injection molding machine, possible to make the material stop valve of a screw conveying tube completely closed when shooting out raw material so as to prevent raw material inside from leaking out along the shaft position base of the hot-material passageway plate by closing the material stop valve and the shaft position base.